Tropical Diseases of Interest to the Radiologist

Abstract

Tropical diseases have been defined as diseases which occur or tend to be more prevalent in tropical and subtropical zones. As a result of modern methods of transportation, however, and the present world conflict, they are seen with increasing frequency in temperate areas. Some of the major factors influencing their usual locale include special climatic conditions essential for the existence of the intermediate hosts or vectors often required for their transmission to man, poor local sanitation, and primitive living conditions. The return of large numbers of infected military and civil personnel from endemic areas may result in a significant incidence of the diseases in this country. In this connection it is well to remember that only three decades ago malaria was a common disease in the United States; typhus is still a common disease in Europe; and cholera and yellow fever are only two generations away as a commonplace in subtropical latitudes. In the present résumé we will attempt to consider the more significant diseases in the approximate order of their present clinical importance in this country, and will also make brief reference to certain diseases not strictly tropical in nature, but of sufficiently greater incidence in some tropical and semitropical areas to warrant consideration here. Malaria Malaria is probably the most important world-wide disease today (1) and is undoubtedly the major medical problem of the present world war. As has often been noted, “it accelerates the decline of nations and vanquishes more soldiers than the enemy” (2). The radiologist is concerned with the disease in this country chiefly as an additional factor for consideration in differential diagnosis. He must recollect that it can mimic a host of diseases involving different organs of the body, resulting in symptoms which may cause a patient to be referred for x-ray examination of almost any region. Most of the victims of malaria can recognize its diverse manifestations and diagnose its recurrences independent of the physician. Some, however, are unaware that they have the disease or may fail to give a history of infection, and such patients can present themselves with any of the following symptoms, precipitated by fatigue, exposure, surgical procedures, and various lesser vicissitudes: (a) Atypical febrile illness, resembling tuberculosis or typhoid. (b) Delirium or convulsions (due to cerebral involvement). (c) Abdominal pain, simulating appendicitis, cholecystitis, and even intestinal obstruction. (d) Diarrhea (malarial dysentery). (e) Pulmonary disturbances, such as bronchitis and pleurisy. (f) Nephritis and hematuria, including blackwater fever. (g) Miscellaneous and bizarre disorders of other organs or parts of the body. The diagnosis must be suspected in order to be made and requires the finding of Plasmodia in the blood smear for confirmation. Plasmodium vivax (causing benign tertian malaria) is the most widely found organism.